George Berkeley

George Berkeley, Bishop of Cloyne, was one of the great philosophers
of the early modern period. He was a brilliant critic of his
predecessors, particularly Descartes, Malebranche, and Locke. He was a
talented metaphysician famous for defending idealism, that is, the
view that reality consists exclusively of minds and their
ideas. Berkeley's system, while it strikes many as counter-intuitive,
is strong and flexible enough to counter most objections. His
most-studied works, the Treatise Concerning the Principles of
Human Knowledge (Principles, for short) and Three
Dialogues between Hylas and Philonous (Dialogues), are
beautifully written and dense with the sort of arguments that delight
contemporary philosophers. He was also a wide-ranging thinker with
interests in religion (which were fundamental to his philosophical
motivations), the psychology of vision, mathematics, physics, morals,
economics, and medicine. Although many of Berkeley's first readers
greeted him with incomprehension, he influenced both Hume and Kant,
and is much read (if little followed) in our own day.

Berkeley was born in 1685 near Kilkenny, Ireland. After several
years of schooling at Kilkenny College, he entered Trinity College, in
Dublin, at age 15. He was made a fellow of Trinity College in
1707 (three years after graduating) and was ordained in the Anglican
Church shortly thereafter. At Trinity, where the curriculum was
notably modern, Berkeley encountered the new science and philosophy of
the late seventeenth century, which was characterized by hostility
towards Aristotelianism. Berkeley's philosophical notebooks
(sometimes styled the Philosophical Commentaries), which he
began in 1707, provide rich documentation of Berkeley's early
philosophical evolution, enabling the reader to track the emergence of
his immaterialist philosophy from a critical response to Descartes,
Locke, Malebranche, Newton, Hobbes, and others.

Berkeley's first important published work, An Essay Towards a New
Theory of Vision (1709), was an influential contribution to the
psychology of vision and also developed doctrines relevant to his
idealist project. In his mid-twenties, he published his most enduring
works, the Treatise concerning the Principles of Human
Knowledge (1710) and the Three Dialogues between Hylas and
Philonous (1713), whose central doctrines we will examine
below.

In 1720, while completing a four-year tour of Europe as tutor to a
young man, Berkeley composed De Motu, a tract on the
philosophical foundations of mechanics which developed his views on
philosophy of science and articulated an instrumentalist approach to
Newtonian dynamics. After his continental tour, Berkeley returned to
Ireland and resumed his position at Trinity until 1724, when he was
appointed Dean of Derry. At this time, Berkeley began developing his
scheme for founding a college in Bermuda. He was convinced that Europe
was in spiritual decay and that the New World offered hope
for a new golden age. Having secured a charter and promises of funding
from the British Parliament, Berkeley set sail for America in 1728,
with his new bride, Anne Forster. They spent three years in Newport,
Rhode Island, awaiting the promised money, but Berkeley's political
support had collapsed and they were forced to abandon the project and
return to Britain in 1731. While in America, Berkeley composed
Alciphron, a work of Christian apologetics directed
against the “free-thinkers” whom he took to be enemies of established
Anglicanism. Alciphron is also a significant philosophical
work and a crucial source of Berkeley's views on language.

Shortly after returning to London, Berkeley composed the Theory
of Vision, Vindicated and Explained, a defense of his earlier
work on vision, and the Analyst, an acute and influential
critique of the foundations of Newton's calculus. In 1734 he was made
Bishop of Cloyne, and thus he returned to Ireland. It was here that
Berkeley wrote his last, strangest, and best-selling (in his own
lifetime) philosophical work. Siris (1744) has a three-fold
aim: to establish the virtues of tar-water (a liquid prepared by
letting pine tar stand in water) as a medical panacea, to provide
scientific background supporting the efficacy of tar-water, and to
lead the mind of the reader, via gradual steps, toward contemplation
of God. Berkeley died in 1753, shortly after moving to Oxford to
supervise the education of his son George, one of the three out of
seven of his children to survive childhood.

In his two great works of metaphysics, Berkeley defends idealism by
attacking the materialist alternative. What exactly is the doctrine
that he's attacking? Readers should first note that
“materialism” is here used to mean “the doctrine
that material things exist”. This is in contrast with another
use, more standard in contemporary discussions, according to which
materialism is the doctrine that only material things
exist. Berkeley contends that no material things exist, not
just that some immaterial things exist. Thus, he attacks Cartesian and
Lockean dualism, not just the considerably less popular (in
Berkeley's time) view, held by Hobbes, that only material things
exist. But what exactly is a material thing? Interestingly, part
of Berkeley's attack on matter is to argue that this question cannot
be satisfactorily answered by the materialists, that they cannot
characterize their supposed material things. However, an answer
that captures what exactly it is that Berkeley rejects is that
material things are mind-independent things or
substances. And a mind-independent thing is something whose existence
is not dependent on thinking/perceiving things, and thus would exist
whether or not any thinking things (minds) existed. Berkeley holds
that there are no such mind-independent things, that, in the famous
phrase, esse est percipi (aut percipere) — to be is to
be perceived (or to perceive).

Berkeley charges that materialism promotes skepticism and atheism:
skepticism because materialism implies that our senses mislead us as
to the natures of these material things, which moreover need not exist
at all, and atheism because a material world could be expected to run
without the assistance of God. This double charge provides Berkeley's
motivation for questioning materialism (one which he thinks
should motivate others as well), though not, of course, a
philosophical argument against materialism. Fortunately, the
Principles and Dialogues overflow with such
arguments. Below, we will examine some of the main elements of
Berkeley's argumentative campaign against matter.

The starting point of Berkeley's attack on the materialism of his
contemporaries is a very short argument presented in
Principles 4:

It is indeed an opinion strangely prevailing amongst men, that
houses, mountains, rivers, and in a word all sensible objects have an
existence natural or real, distinct from their being perceived by the
understanding. But with how great an assurance and acquiescence soever
this principle may be entertained in the world; yet whoever shall find
in his heart to call it in question, may, if I mistake not, perceive it
to involve a manifest contradiction. For what are the forementioned
objects but the things we perceive by sense, and what do we perceive
besides our own ideas or sensations; and is it not plainly repugnant
that any one of these or any combination of them should exist
unperceived?

The argument is valid, and premise (1) looks hard to deny. What
about premise (2)? Berkeley believes that this premise is accepted by
all the modern philosophers. In the Principles, Berkeley is
operating within the idea-theoretic tradition of the
seventeenth and eighteenth centuries. In particular, Berkeley believes
that some version of this premise is accepted by his main targets, the
influential philosophers Descartes and Locke.

However, Berkeley recognizes that these philosophers have an obvious
response available to this argument. This response blocks Berkeley's
inference to (3) by distinguishing two sorts of perception, mediate
and immediate. Thus, premises (1) and (2) are replaced by the claims
that (1′) we mediately perceive ordinary objects, while
(2′) we immediately perceive only ideas. From these claims, of
course, no idealist conclusion follows. The response reflects a
representationalist theory of perception, according to which
we indirectly (mediately) perceive material things, by directly
(immediately) perceiving ideas, which are mind-dependent items. The
ideas represent external material objects, and thereby allow
us to perceive them.

Whether Descartes, Malebranche, and Locke were representationalists
of this kind is a matter of some controversy (see e.g. Yolton 1984,
Chappell 1994). However, Berkeley surely had good grounds for
understanding his predecessors in this way: it reflects the most
obvious interpretation of Locke's account of perception and
Descartes' whole procedure in the Meditations tends to
suggest this sort of view, given the meditator's situation as someone
contemplating her own ideas, trying to determine whether something
external corresponds to them.

Berkeley devotes the succeeding sections of the Principles
to undermining the representationalist response to his initial
argument. In effect, he poses the question: What allows an idea to
represent a material object? He assumes, again with good grounds,
that the representationalist answer is going to involve
resemblance:

But say you, though the ideas themselves do not exist without the
mind, yet there may be things like them whereof they are copies or
resemblances, which things exist without the mind, in an unthinking
substance. I answer, an idea can be like nothing but an idea; a colour
or figure can be like nothing but another colour or figure. (PHK
8)

Berkeley argues that this supposed resemblance is nonsensical; an
idea can only be like another idea.

But why? The closest Berkeley ever comes to directly addressing this
question is in his early philosophical notebooks, where he observes
that “Two things cannot be said to be alike or unlike till they
have been compar'd” (PC 377). Thus, because the mind can compare
nothing but its own ideas, which by hypothesis are the only things
immediately perceivable, the representationalist cannot assert a
likeness between an idea and a non-ideal mind-independent material
object. (For further discussion, see Winkler 1989, 145–9.)

If Berkeley's Likeness Principle, the thesis that an idea can only be
like another idea, is granted, representationalist materialism is in
serious trouble. For how are material objects now to be characterized?
If material objects are supposed to be extended, solid, or colored,
Berkeley will counter that these sensory qualities pertain to ideas,
to that which is immediately perceived, and that the materialist
cannot assert that material objects are like ideas in these ways. Many
passages in the Principles and Dialogues drive home
this point, arguing that matter is, if not an incoherent notion, at
best a completely empty one.

One way in which Berkeley's anti-abstractionism comes into play is in
reinforcing this point. Berkeley argues in the
“Introduction” to the
Principles[1]
that we cannot form general ideas in the way that Locke often seems
to suggest—by stripping particularizing qualities from an idea
of a particular, creating a new, intrinsically general,
abstract
idea.[2]
Berkeley then claims that notions the materialist might invoke in a
last-ditch attempt to characterize matter, e.g. being or mere
extension, are objectionably abstract and
unavailable.[3]

Berkeley is aware that the materialist has one important card left to
play: Don't we need material objects in order to explain our
ideas? And indeed, this seems intuitively gripping: Surely the best
explanation of the fact that I have a chair idea every time I enter my
office and that my colleague has a chair idea when she enters
my office is that a single enduring material object causes
all these various ideas. Again, however, Berkeley replies by
effectively exploiting the weaknesses of his opponents' theories:

…though we give the materialists their external bodies, they
by their own confession are never the nearer knowing how our ideas are
produced: since they own themselves unable to comprehend in what manner
body can act upon spirit, or how it is possible it should imprint any
idea in the mind. Hence it is evident the production of ideas or
sensations in our minds, can be no reason why we should suppose matter
or corporeal substances, since that is acknowledged to remain equally
inexplicable with, or without this supposition. (PHK 19)

Firstly, Berkeley contends, a representationalist must admit that we
could have our ideas without there being any external objects
causing them (PHK 18). (This is one way in which Berkeley sees
materialism as leading to skepticism.) More devastatingly, however,
he must admit that the existence of matter does not help to explain
the occurrence of our ideas. After all, Locke himself diagnosed the
difficulty:

Body as far as we can conceive being able only to strike and affect
body; and Motion, according to the utmost reach of our Ideas,
being able to produce nothing but Motion, so that when we allow it to
produce pleasure or pain, or the Idea of a Colour, or Sound,
we are fain to quit our Reason, go beyond our Ideas, and
attribute it wholly to the good Pleasure of our Maker. (Locke 1975,
541;Essay 4.3.6)

And, when Descartes was pressed by Elizabeth as to how mind
and body
interact,[4]
she rightly regarded his answers as unsatisfactory. The basic problem
here is set by dualism: how can one substance causally affect another
substance of a fundamentally different kind? In its
Cartesian form, the difficulty is particularly severe: how can an
extended thing, which affects other extended things only by mechanical
impact, affect a mind, which is non-extended and
non-spatial?

Berkeley's point is thus well taken. It is worth noting that, in
addition to undermining the materialist's attempted inference to the
best explanation, Berkeley's point also challenges any attempt to
explain representation and mediate perception in terms of
causation. That is, the materialist might try to claim that ideas
represent material objects, not by resemblance, but in virtue of being
caused by the objects. (Though neither Descartes nor Locke
spells out such an account, there are grounds in each for attributing
such an account to them. For Descartes see Wilson 1999, 73–76; for
Locke see Chappell 1994, 53.) However, PHK 19 implies that the
materialists are not in a position to render this account of
representation philosophically satisfactory.

As emphasized above, Berkeley's campaign against matter, as he
presents it in the Principles, is directed against
materialist representationalism and presupposes
representationalism. In particular, Berkeley presupposes that all
anyone ever directly or immediately perceives are ideas. As
contemporary philosophers, we might wonder whether Berkeley has
anything to say to a materialist who denies this representationalist
premise and asserts instead that we ordinarily directly/immediately
perceive material objects themselves. The answer is
‘yes’.

However, one place where one might naturally look for such an
argument is not, in fact, as promising as might initially appear. In
both the Principles (22–3) and the Dialogues (200),
Berkeley gives a version of what has come to be called “The
Master
Argument”[5]
because of the apparent strength with which he endorses it:

… I am content to put the whole upon this issue; if you can
but conceive it possible for one extended moveable substance, or in
general, for any one idea or any thing like an idea, to exist
otherwise than in a mind perceiving it, I shall readily give up the
cause…. But say you, surely there is nothing easier than to
imagine trees, for instance, in a park, or books existing in a closet,
and no body by to perceive them. I answer, you may so, there is no
difficulty in it: but what is all this, I beseech you, more than
framing in your mind certain ideas which you call books and
trees, and at the same time omitting to frame the idea of any
one that may perceive them? But do not you your self perceive or think
of them all the while? This therefore is nothing to the purpose: it
only shows you have the power of imagining or forming ideas in your
mind; but it doth not shew that you can conceive it possible, the
objects of your thought may exist without the mind: to make out this,
it is necessary that you conceive them existing unconceived or
unthought of, which is a manifest repugnancy. When we do our utmost to
conceive the existence of external bodies, we are all the while only
contemplating our own ideas. But the mind taking no notice of itself,
is deluded to think it can and doth conceive bodies existing unthought
of or without the mind; though at the same time they are apprehended
by or exist in it self. (PHK 22–23)

The argument seems intended to establish that we cannot actually
conceive of mind-independent objects, that is, objects existing
unperceived and unthought of. Why not? Simply because in order to
conceive of any such things, we must ourselves be conceiving,
i.e., thinking, of them. However, as Pitcher (1977, 113) nicely observes,
such an argument seems to conflate the representation (what
we conceive with) and the represented (what we
conceive of—the content of our thought). Once we make
this distinction, we realize that although we must have some
conception or representation in order to conceive of something, and
that representation is in some sense thought of, it does not
follow (contra Berkeley) that what we conceive of must be a
thought-of object. That is, when we imagine a tree standing alone in a
forest, we (arguably) conceive of an unthought-of object, though of
course we must employ a thought in order to accomplish this
feat.[6]
Thus (as many commentators have observed), this argument
fails.

A more charitable reading of the argument (see Winkler 1989, 184–7;
Lennon 1988) makes Berkeley's point that we cannot represent
unconceivedness, because we have never and could never experience
it.[7]
Because we cannot represent unconceivedness, we cannot conceive of
mind-independent objects. While this is a rather more promising
argument, it clearly presupposes representationalism, just as
Berkeley's earlier Principles arguments
did.[8]
(This, however, is not necessarily a defect of the interpretation,
since the Principles, as we saw above, is aimed against
representationalism, and in the Dialogues the Master Argument
crops up only after Hylas has been converted to representationalism
(see
below).)[9]

Thus, if we seek a challenge to direct realist materialism, we must
turn to the Three Dialogues, where the character Hylas (the
would-be materialist) begins from a sort of naïve realism,
according to which we perceive material objects themselves,
directly. Against this position, Philonous (lover of
spirit—Berkeley's spokesperson) attempts to argue that the
sensible qualities—the qualities immediately perceived by
sense—must be ideal, rather than belonging to material
objects. (The following analysis of these first dialogue arguments is
indebted to Margaret Wilson's account in “Berkeley on the
Mind-Dependence of Colors,” Wilson 1999,
229–242.[10])

Philonous begins his first argument by contending that sensible
qualities such as heat are not distinct from pleasure or pain.
Pleasure and pain, Philonous argues, are allowed by all to be merely
in the mind; therefore the same must be true for the sensible
qualities. The most serious difficulties with this argument are (1)
whether we should grant the “no distinction” premise in
the case of the particular sensory qualities invoked by Berkeley (why
not suppose that I can distinguish between the heat and the pain?)
and (2) if we do, whether we should generalize to all sensory
qualities as Berkeley would have us do.

Secondly, Philonous invokes relativity arguments to suggest that
because sensory qualities are relative to the perceiver, e.g. what is
hot to one hand may be cold to the other and what is sweet to one
person may be bitter to another, they cannot belong to
mind-independent material objects, for such objects could not bear
contradictory qualities.

As Berkeley is well aware, one may reply to this sort of argument by
claiming that only one of the incompatible qualities is truly a
quality of the object and that the other apparent qualities result
from misperception. But how then, Berkeley asks, are these
“true” qualities to be identified and distinguished from
the “false” ones (3D 184)? By noting the differences
between animal perception and human perception, Berkeley suggests that
it would be arbitrary anthropocentrism to claim that humans have
special access to the true qualities of objects. Further, Berkeley
uses the example of microscopes to undermine the prima facie
plausible thought that the true visual qualities of objects are
revealed by close examination. Thus, Berkeley provides a strong
challenge to any direct realist attempt to specify standard conditions
under which the true (mind-independent) qualities of objects are
(directly) perceived by sense.

Under this pressure from Philonous, Hylas retreats (perhaps a bit
quickly) from naïve realism to a more “philosophical”
position. He first tries to make use of the primary/secondary quality
distinction associated with mechanism and, again, locatable in the
thought of Descartes and Locke. Thus, Hylas allows that color, taste,
etc. may be mind-dependent (secondary) qualities, but contends that
figure, solidity, motion and rest (the primary qualities) exist in
mind-independent material bodies. The mechanist picture behind this
proposal is that bodies are composed of particles with size, shape,
motion/rest, and perhaps solidity, and that our sensory ideas arise
from the action of such particles on our sense organs and, ultimately,
on our minds. Berkeley opposes this sort of mechanism throughout his
writings, believing that it engenders skepticism by dictating that
bodies are utterly unlike our sensory experience of them. Here
Philonous has a two-pronged reply: (1) The same sorts of relativity
arguments that were made against secondary qualities can be made
against primary ones. (2) We cannot abstract the primary qualities
(e.g. shape) from secondary ones (e.g. color), and thus we cannot
conceive of mechanist material bodies which are extended but not (in
themselves)
colored.[11]

When, after some further struggles, Hylas finally capitulates to
Philonous' view that all of existence is mind-dependent, he does so
unhappily and with great reluctance. Philonous needs to convince him
(as Berkeley needed to convince his readers in both books) that a
commonsensical philosophy could be built on an immaterialist
foundation, that no one but a skeptic or atheist would ever miss
matter. As a matter of historical fact, Berkeley persuaded few of his
contemporaries, who for the most part regarded him as a purveyor of
skeptical paradoxes (Bracken 1965). Nevertheless, we can and should
appreciate the way in which Berkeley articulated a positive idealist
philosophical system, which, if not in perfect accord with common
sense, is in many respects superior to its competitors.

The basics of Berkeley's metaphysics are apparent from the first
section of the main body of the Principles:

It is evident to any one who takes a survey of the objects of human
knowledge, that they are either ideas actually imprinted on the
senses, or else such as are perceived by attending to the passions and
operations of the mind, or lastly ideas formed by help of memory and
imagination, either compounding, dividing, or barely representing
those originally perceived in the aforesaid ways. By sight I have the
ideas of light and colours with their several degrees and
variations. By touch I perceive, for example, hard and soft, heat and
cold, motion and resistance, and of all these more and less either as
to quantity or degree. Smelling furnishes me with odours; the palate
with tastes, and hearing conveys sounds to the mind in all their
variety of tone and composition. And as several of these are observed
to accompany each other, they come to be marked by one name, and so to
be reputed as one thing. Thus, for example, a certain colour, taste,
smell, figure and consistence having been observed to go together, are
accounted one distinct thing, signified by the name apple. Other
collections of ideas constitute a stone, a tree, a book, and the like
sensible things; which, as they are pleasing or disagreeable, excite
the passions of love, hatred, joy, grief, and so forth.

As this passage illustrates, Berkeley does not deny the existence of
ordinary objects such as stones, trees, books, and apples. On the
contrary, as was indicated above, he holds that only an immaterialist
account of such objects can avoid skepticism about their existence and
nature. What such objects turn out to be, on his account, are bundles
or collections of ideas. An apple is a combination of visual ideas
(including the sensible qualities of color and visual shape), tangible
ideas, ideas of taste, smell,
etc.[12]
The question of what does the combining is a philosophically
interesting one which Berkeley does not address in detail. He does
make clear that there are two sides to the process of bundling ideas
into objects: (1) co-occurrence, an objective fact about what sorts of
ideas tend to accompany each other in our experience, and (2) something we
do when we decide to single out a set of co-occurring ideas and refer
to it with a certain name (NTV 109).

Thus, although there is no material world for Berkeley, there is a
physical world, a world of ordinary objects. This world is
mind-dependent, for it is composed of ideas, whose existence consists
in being perceived. For ideas, and so for the physical world, esse
est percipi.

Berkeley's ontology is not exhausted by the ideal, however. In
addition to perceived things (ideas), he posits perceivers, i.e., minds
or spirits, as he often terms them. Spirits, he emphasizes,
are totally different in kind from ideas, for they are active where
ideas are passive. This suggests that Berkeley has replaced one kind
of dualism, of mind and matter, with another kind of dualism, of mind
and idea. There is something to this point, given Berkeley's refusal
to elaborate upon the relation between active minds and passive
ideas. At Principles 49, he famously dismisses quibbling about
how ideas inhere in the mind (are minds colored and extended
when such sensible qualities “exist in” them?) with the
declaration that “those qualities are in the mind only as they
are perceived by it, that is, not by way of mode or
attribute, but only by way of idea”. Berkeley's
dualism, however, is a dualism within the realm of the
mind-dependent.

The last major item in Berkeley's ontology is God, himself a spirit,
but an infinite one. Berkeley believes that once he has established
idealism, he has a novel and convincing argument for God's existence
as the cause of our sensory ideas. He argues by elimination: What
could cause my sensory ideas? Candidate causes, supposing that
Berkeley has already established that matter doesn't exist, are (1)
other ideas, (2) myself, or (3) some other spirit. Berkeley eliminates
the first option with the following argument (PHK 25):

(1) Ideas are manifestly passive—no power or activity is
perceived in them.

(2) But because of the mind-dependent status of ideas, they cannot
have any characteristics which they are not perceived to have.

Therefore,

(3) Ideas are passive, that is, they possess no causal
power.

It should be noted that premise (2) is rather strong; Phillip Cummins
(1990) identifies it as Berkeley's “manifest qualities
thesis” and argues that it commits Berkeley to the view that
ideas are radically and completely dependent on perceivers in the way
that sensations of pleasure and pain are typically taken to
be.[13]

The second option is eliminated with the observation that although I
clearly can cause some ideas at will (e.g. ideas of imagination),
sensory ideas are involuntary; they present themselves whether I wish
to perceive them or not and I cannot control their content. The hidden
assumption here is that any causing the mind does must be done by
willing and such willing must be accessible to consciousness.
Berkeley is hardly alone in presupposing this model of the mental;
Descartes, for example, makes a similar set of assumptions.

This leaves us, then, with the third option: my sensory ideas must be
caused by some other spirit. Berkeley thinks that when we consider the
stunning complexity and systematicity of our sensory ideas, we must
conclude that the spirit in question is wise and benevolent beyond
measure, that, in short, he is God.

With the basic ingredients of Berkeley's ontology in place, we can
begin to consider how his system works by seeing how he responds to a
number of intuitively compelling objections to it. Berkeley himself
sees very well how necessary this is: Much of the Principles
is structured as a series of objections and replies, and in the
Three Dialogues, once Philonous has rendered Hylas a
reluctant convert to idealism, he devotes the rest of the book to
convincing him that this is a philosophy which coheres well with
common sense, at least better than materialism ever did.

Perhaps the most obvious objection to idealism is that it makes real
things no different from imaginary ones—both seem fleeting
figments of our own minds, rather than the solid objects of the
materialists. Berkeley replies that the distinction between real
things and chimeras retains its full force on his view. One way of
making the distinction is suggested by his argument for the existence
of God, examined above: Ideas which depend on our own finite human
wills are not (constituents of) real things. Not being voluntary is
thus a necessary condition for being a real thing, but it is clearly
not sufficient, since hallucinations and dreams do not depend on our
wills, but are nevertheless not real. Berkeley notes that the ideas
that constitute real things exhibit a steadiness, vivacity, and
distinctness that chimerical ideas do not. The most crucial feature
that he points to, however, is order. The ideas imprinted by
the author of nature as part of rerum natura occur in regular
patterns, according to the laws of nature (“the set rules or
established methods, wherein the mind we depend on excites in us the
ideas of sense, are called the Laws of Nature” PHK 30). They are
thus regular and coherent, that is, they constitute a coherent real
world.

The related notions of regularity and of the laws of nature are
central to the workability of Berkeley's idealism. They allow him to
respond to the following objection, put forward in PHK 60:

…it will be demanded to what purpose serves that curious
organization of plants, and the admirable mechanism in the parts of
animals; might not vegetables grow, and shoot forth leaves and
blossoms, and animals perform all their motions, as well without as
with all that variety of internal parts so elegantly contrived and put
together, which being ideas have nothing powerful or operative in
them, nor have any necessary connexion with the effects ascribed to
them? […] And how comes it to pass, that whenever there is any
fault in the going of a watch, there is some corresponding disorder to
be found in the movements, which being mended by a skilful hand, all
is right again? The like may be said of all the clockwork of Nature,
great part whereof is so wonderfully fine and subtle, as scarce to be
discerned by the best microscope. In short, it will be asked, how upon
our principles any tolerable account can be given, or any final cause
assigned of an innumerable multitude of bodies and machines framed
with the most exquisite art, which in the common philosophy have very
apposite uses assigned them, and serve to explain abundance of
phenomena.

Berkeley's answer, for which he is indebted to
Malebranche,[14]
is that, although God could make a watch run (that is, produce in us
ideas of a watch running) without the watch having any internal
mechanism (that is, without it being the case that, were we to open
the watch, we would have ideas of an internal mechanism), he cannot do
so if he is to act in accordance with the laws of nature, which he has
established for our benefit, to make the world regular and
predictable. Thus, whenever we have ideas of a working watch, we will
find that if we open
it,[15]
we will see (have ideas of) an appropriate internal
mechanism. Likewise, when we have ideas of a living tulip, we will
find that if we pull it apart, we will observe the usual internal
structure of such plants, with the same transport tissues,
reproductive parts, etc.

Implicit in the answer above is Berkeley's insightful account of
scientific explanation and the aims of science. A bit of background is
needed here to see why this issue posed a special challenge for
Berkeley. One traditional understanding of science, derived from
Aristotle, held that it aims at identifying the causes of
things. Modern natural philosophers such as Descartes narrowed
science's domain to efficient causes and thus held that
science should reveal the efficient causes of natural things,
processes, and
events.[16]
Berkeley considers this as the source of an objection at Principles
51:

Seventhly, it will upon this be demanded whether it does not seem
absurd to take away natural causes, and ascribe every thing to the
immediate operation of spirits? We must no longer say upon these
principles that fire heats, or water cools, but that a spirit heats,
and so forth. Would not a man be deservedly laughed at, who should
talk after this manner? I answer, he would so; in such things we ought
to think with the learned, and speak with the vulgar.

On Berkeley's account, the true cause of any phenomenon is a
spirit, and most often it is the same spirit, namely, God.

But surely, one might object, it is a step backwards to abandon our
scientific theories and simply note that God causes what happens in
the physical world! Berkeley's first response here, that we should
think with the learned but speak with the vulgar, advises us to
continue to say that fire heats, that the heart pumps blood, etc.
What makes this advice legitimate is that he can reconstrue such talk
as being about regularities in our ideas. In Berkeley's view, the
point of scientific inquiry is to reveal such regularities:

If therefore we consider the difference there is betwixt natural
philosophers and other men, with regard to their knowledge of the
phenomena, we shall find it consists, not in an exacter
knowledge of the efficient cause that produces them, for that can be
no other than the will of a spirit, but only in a greater
largeness of comprehension, whereby analogies, harmonies, and
agreements are discovered in the works of Nature, and the particular
effects explained, that is, reduced to general rules, see
Sect. 62, which rules grounded on the analogy, and
uniformness observed in the production of natural effects, are most
agreeable, and sought after by the mind; for that they extend our
prospect beyond what is present, and near to us, and enable us to make
very probable conjectures, touching things that may have happened at
very great distances of time and place, as well as to predict things
to come…. (PHK 105)

Natural philosophers thus consider signs, rather than causes (PHK
108), but their results are just as useful as they would be under a
materialist system. Moreover, the regularities they discover provide
the sort of explanation proper to science, by rendering the particular
events they subsume unsurprising (PHK 104). The sort of explanation
proper to science, then, is not causal explanation, but reduction to
regularity.[17]

Regularity provides a foundation for one of Berkeley's responses
to the objection summarized in the famous limerick:

There was a young man who said God,
must think it exceedingly odd
if he finds that the tree
continues to be
when no one's about in the
Quad.[18]

The worry, of course, is that if to be is to be perceived (for
non-spirits), then there are no trees in the Quad at 3 a.m. when no
one is there to perceive them and there is no furniture in my office
when I leave and close the door. Interestingly, in the
Principles Berkeley seems relatively unperturbed by this
natural objection to idealism. He claims that there is no problem
for

…anyone that shall attend to what is meant by the term
exist when applied to sensible things. The table I write
on, I say, exists, that is, I see and feel it; and if I were out of my
study I should say it existed, meaning thereby that if I was in my
study I might perceive it, or that some other spirit actually does
perceive it. (PHK 3)

So, when I say that my desk still exists after I leave my office,
perhaps I just mean that I would perceive it if I were in my office,
or, more broadly, that a finite mind would perceive the desk were it
in the appropriate circumstances (in my office, with the lights on,
with eyes open, etc.). This is to provide a sort of counterfactual
analysis of the continued existence of unperceived objects. The truth
of the counterfactuals in question is anchored in regularity: because
God follows set patterns in the way he causes ideas, I would have a
desk idea if I were in the office.

Unfortunately, this analysis has counterintuitive consequences when
coupled with the esse est percipi doctrine (McCracken 1979,
286). If to be is, as Berkeley insists, to be perceived, then the
unperceived desk does not exist, despite the fact that it
would be perceived and thus would exist if someone
opened the office door. Consequently, on this view the desk would not
endure uninterrupted but would pop in and out of existence, though it
would do so quite predictably. One way to respond to this worry would
be to dismiss it—what does it matter if the desk ceases to exist
when unperceived, as long as it exists whenever we need it? Berkeley
shows signs of this sort of attitude in Principles 45–46, where he
tries to argue that his materialist opponents and scholastic
predecessors are in much the same
boat.[19]
This “who cares?” response to the problem of continued
existence is fair enough as far as it goes, but it surely does
conflict with common sense, so if Berkeley were to take this route he
would have to moderate his claims about his system's ability to
accommodate everything desired by the person on the street.

Another strategy, however, is suggested by Berkeley's reference in
PHK 3 and 48 to “some other spirit,” a strategy
summarized in a further limerick:

Dear Sir, your astonishment's odd
I am always about in the Quad
And that's why the tree
continues to be
since observed by, Yours faithfully, God

If the other spirit in question is God, an omnipresent being, then
perhaps his perception can be used to guarantee a completely
continuous existence to every physical object. In the Three
Dialogues, Berkeley very clearly invokes God in this
context. Interestingly, whereas in the Principles, as we have
seen above, he argued that God must exist in order to cause
our ideas of sense, in the Dialogues (212, 214–5) he argues
that our ideas must exist in God when not perceived by
us.[20]
If our ideas exist in God, then they presumably exist
continuously. Indeed, they must exist continuously, since standard
Christian doctrine dictates that God is unchanging.

Although this solves one problem for Berkeley, it creates several
more. The first is that Berkeley's other commitments, religious and
philosophical, dictate that God cannot literally have our ideas. Our
ideas are sensory ideas and God is a being who “can suffer
nothing, nor be affected with any painful sensation, or indeed any
sensation at all” (3D 206). Nor can our sensory ideas be copies
of God's nonsensory ones (McCracken 1979):

How can that which is sensible be like that which is insensible? Can
a real thing in itself invisible be like a colour;
or a real thing which is not audible, be like a
sound? (3D 206)

A second problem is that God's ideas are eternal, whereas physical
objects typically have finite duration. And, even worse, God has ideas
of all possible objects (Pitcher 1977, 171–2), not just the ones which
we would commonsensically wish to say exist.

A solution (proposed by McCracken) to these related problems is to
tie the continued existence of ordinary objects to God's will, rather
than to his understanding. McCracken's suggestion is that unperceived
objects continue to exist as God's decrees. Such an account in terms
of divine decrees or volitions looks promising: The tree continues to
exist when unperceived just in case God has an appropriate volition or
intention to cause a tree-idea in finite perceivers under the right
circumstances. Furthermore, this solution has important textual
support: In the Three Dialogues, Hylas challenges Philonous
to account for the creation, given that all existence is
mind-dependent, in his view, but everything must exist eternally in
the mind of God. Philonous responds as follows:

May we not understand it [the creation] to have been entirely in
respect of finite spirits; so that things, with regard to us, may
properly be said to begin their existence, or be created, when God
decreed they should become perceptible to intelligent creatures, in
that order and manner which he then established, and we now call the
laws of Nature? You may call this a relative, or
hypothetical existence if you please. (3D 253)

Here Berkeley ties the actual existence of created physical beings to
God's decrees, that is, to his will.

As with the counterfactual analysis of continued existence, however,
this account also fails under pressure from the esse est
percipi principle:

Hylas. Yes, Philonous, I grant the existence of a sensible thing consists
in being perceivable, but not in being actually perceived.

Philonous. And what is perceivable but an idea? And can an
idea exist without being actually perceived? These are points
long since agreed between us. (3D 234)

Thus, if the only grounds of continued existence are
volitions in God's mind, rather than perceived items (ideas),
then ordinary objects do not exist continuously, but rather pop in and
out of existence in a lawful fashion.

Fortunately, Kenneth Winkler has put forward an interpretation which
goes a great distance towards resolving this difficulty. In effect, he
proposes that we amend the “volitional” interpretation of
the existence of objects with the hypothesis that Berkeley held
“the denial of blind agency” (Winkler 1989, 207–224). This
principle, which can be found in many authors of the period (including
Locke), dictates that any volition must have an idea behind it, that
is, must have a cognitive component that gives content to the
volition, which would otherwise be empty or “blind”. While
the principle is never explicitly invoked or argued for by Berkeley,
in a number of passages he does note the interdependence of will and
understanding. Winkler plausibly suggests that Berkeley may have found
this principle so obvious as to need no arguing. With it in place, we
have a guarantee that anything willed by God, e.g. that finite
perceivers in appropriate circumstances should have elm tree ideas,
also has a divine idea associated with it. Furthermore, we have a neat
explanation of Berkeley's above-noted leap in the Dialogues
from the claim that God must cause our ideas to the claim that our
ideas must exist in God.

Of course, it remains true that God cannot have ideas that are,
strictly speaking, the same as ours. This problem is closely related
to another that confronts Berkeley: Can two people ever perceive the
same thing? Common sense demands that two students can perceive the
same tree, but Berkeley's metaphysics seems to dictate that they never
truly perceive the same thing, since they each have their own
numerically distinct ideas. One way to dissolve this difficulty is to
recall that objects are bundles of ideas. Although two people cannot
perceive/have the numerically same idea, they can perceive the same
object, assuming that perceiving a component of the bundle suffices
for perception of the
bundle.[21]
Another proposal (Baxter 1991) is to invoke Berkeley's doctrine that
“same” has both a philosophical and a vulgar sense (3D
247) in order to declare that my tree-idea and your tree-idea are
strictly distinct but loosely (vulgarly) the same. Either account
might be applied in order to show either that God and I may perceive
the same object, or that God and I may perceive, loosely speaking, the
same thing.

From this discussion we may draw a criterion for the actual existence
of ordinary objects, one which summarizes Berkeley's considered
views:

An X exists at time t if and only if God has an
idea that corresponds to a volition that if a finite mind at
t is in appropriate circumstances (e.g. in a particular
place, looking in the right direction, or looking through a
microscope), then it will have an idea that we would be disposed to
call a perception of an X.

This captures the idea that
existence depends on God's perceptions, but only on the perceptions
which correspond to or are included in his volitions about what
we should perceive. It also captures the fact that the
bundling of ideas into objects is done by
us.[22]

A further worry about Berkeley's system arises from the
idea-bundle account of
objects.[23]
If there is no mind-independent object against which to measure my
ideas, but rather my ideas help to constitute the object, then how can
my ideas ever fail—how is error possible? Here is another way
to raise the worry that I have in mind: We saw above that
Berkeley's arguments against commonsense realism in the first
Dialogue attempt to undermine (1) claims that heat, odor,
taste are distinguishable from pleasure/pain and (2) the claim that
objects have one true color, one true shape, one true taste, etc. If
we then consider what this implies about Berkeleyian objects, we must
conclude that Berkeley's cherry is red, purple, gray, tart, sweet,
small, large, pleasant, and painful! It seems that Berkeley's desire
to refute the mechanist representationalism which dictates that
objects are utterly unlike our experience of them has lead
him to push beyond common sense to the view that objects are
exactly like our experience of
them.[24]
There is no denying that Berkeley is out of sync with common sense
here. He does, however, have an account of error, as he shows us in
the Dialogues:

Hylas. What say you to this? Since, according to you, men judge of
the reality of things by their senses, how can a man be mistaken in
thinking the moon a plain lucid surface, about a foot in diameter; or a
square tower, seen at a distance, round; or an oar, with one end in the
water, crooked?

Philonous. He is not mistaken with regard to the ideas he actually
perceives; but in the inferences he makes from his present perceptions.
Thus in the case of the oar, what he immediately perceives by sight is
certainly crooked; and so far he is in the right. But if he thence
conclude, that upon taking the oar out of the water he shall perceive
the same crookedness; or that it would affect his touch, as crooked
things are wont to do: in that he is mistaken. (3D 238)

Extrapolating from this, we may say that my gray idea of the cherry,
formed in dim light, is not in itself wrong and forms a part of the
bundle-object just as much as your red idea, formed in daylight.
However, if I judge that the cherry would look gray in bright light,
I'm in error. Furthermore, following Berkeley's directive to speak
with the vulgar, I ought not to say (in ordinary circumstances) that
“the cherry is gray,” since that will be taken to imply
that the cherry would look gray to humans in daylight.

We have spent some time examining the difficulties Berkeley faces in
the “idea/ordinary object” half of his ontology.
Arguably, however, less tractable difficulties confront him in the
realm of spirits. Early on, Berkeley attempts to forestall materialist
skeptics who object that we have no idea of spirit by arguing for this
position himself:

A spirit is one simple, undivided, active being: as it perceives
ideas, it is called the understanding, and as it produces or
otherwise operates about them, it is called the will. Hence
there can be no idea formed of a soul or spirit: for all ideas
whatever, being passive and inert, vide Sect. 25, they cannot
represent unto us, by way of image or likeness, that which acts. A
little attention will make it plain to any one, that to have an idea
which shall be like that active principle of motion and change of
ideas, is absolutely impossible. Such is the nature of spirit or that
which acts, that it cannot be of it self perceived, but only by the
effects which it produceth. (PHK 27)

Surely the materialist will be tempted to complain, however, that
Berkeley's unperceivable spiritual substances, lurking behind the
scenes and supporting that which we can perceive, sound a lot like the
material substances which he so emphatically rejects.

Two very different responses are available to Berkeley on this issue,
each of which he seems to have made at a different point in his
philosophical development. One response would be to reject spiritual
substance just as he rejected material substance. Spirits, then,
might be understood in a Humean way, as bundles of ideas and
volitions. Fascinatingly, something like this view is considered by
Berkeley in his early philosophical notebooks (see PC 577ff). Why he
abandons it is an interesting and difficult
question;[25]
it seems that one worry he has is how the understanding and the will
are to be integrated and rendered one thing.

The second response would be to explain why spiritual substances are
better posits than material ones. To this end, Berkeley emphasizes
that we have a notion of spirit, which is just to say that we know
what the word means. This purportedly contrasts with
“matter,” which Berkeley thinks has no determinate
content. Of course, the real question is: How does the term
“spirit” come by any content, given that we have no idea
of it? In the Principles, Berkeley declares only that we
know spirit through our own case and that the content we assign to
“spirit” is derived from the content each of us assigns to
“I” (PHK 139–140). In the Dialogues, however,
Berkeley shows a better appreciation of the force of the problem that
confronts him:

[Hylas.] You say your own soul supplies you with some sort of
an idea or image of God. But at the same time you acknowledge you have,
properly speaking, no idea of your own soul. You even affirm that
spirits are a sort of beings altogether different from ideas.
Consequently that no idea can be like a spirit. We have therefore no
idea of any spirit. You admit nevertheless that there is spiritual
substance, although you have no idea of it; while you deny there can be
such a thing as material substance, because you have no notion or idea
of it. Is this fair dealing? To act consistently, you must either admit
matter or reject spirit. (3D 232)

To the main point of Hylas' attack, Philonous replies that each of us
has, in our own case, an immediate intuition of ourselves, that is, we
know our own minds through reflection (3D 231–233). Berkeley's
considered position, that we gain access to ourselves as thinking
things through conscious awareness, is surely an intuitive
one. Nevertheless, it is disappointing that he never gave an explicit
response to the Humean challenge he entertained in his notebooks:

+ Mind is a congeries of Perceptions. Take away Perceptions
& you take away the Mind put the Perceptions & you put the
mind. (PC 580)

A closely related problem which confronts Berkeley is how to make
sense of the causal powers that he ascribes to spirits. Here again,
the notebooks suggest a surprisingly Humean view:

+ The simple idea call'd Power seems obscure or rather none at all. but
onely the relation ‘twixt cause & Effect. Wn I ask whether A can
move B. if A be an intelligent thing. I mean no more than whether the
volition of A that B move be attended with the motion of B, if A be
senseless whether the impulse of A against B be follow'd by ye motion
of B.
461[26]

S What means Cause as distinguish'd from Occasion? nothing but a Being
wch wills wn the Effect follows the volition. Those things that happen
from without we are not the Cause of therefore there is some other
Cause of them i.e., there is a being that wills these perceptions in
us. 499

S There is a difference betwixt Power & Volition. There may be
volition without Power. But there can be no Power without Volition.
Power implyeth volition & at the same time a Connotation of the
Effects following the Volition. 699

461 suggests the Humean view that a cause is whatever is
(regularly)[27]
followed by an effect. 499 and 699 revise this doctrine by requiring
that a cause not only (regularly) precede an effect but also be a
volition. Berkeley's talk of occasion here reveals the immediate
influence of Malebranche. Malebranche held that the only true cause
is God and that apparent finite causes are only “occasional
causes,” which is to say that they provide occasions for God to
act on his general volitional policies. Occasional
“causes” thus regularly precede their
“effects” but are not truly responsible for producing
them. In these notebook entries, however, Berkeley seems to be
suggesting that all there is to causality is this regular consequence,
with the first item being a volition. Such an account, unlike
Malebranche's, would make my will and God's will causes in exactly the
same thin sense.

Some commentators, most notably Winkler, suppose that Berkeley
retains this view of causality in the published works. The main
difficulty with this interpretation is that Berkeley more than once
purports to inspect our idea of body, and the sensory qualities
included therein, and to conclude from that inspection that bodies are
passive (DM 22, PHK 25). This procedure would make little sense if
bodies, according to Berkeley, fail to be causes by definition, simply
because they are not minds with
wills.[28]
What is needed is an explanation of what Berkeley means by
activity, which he clearly equates with causal power. Winkler (1989,
130–1) supplies such an account, according to which activity means
direction towards an end. But this is to identify efficient causation
with final causation, a controversial move at best which Berkeley
would be making without comment or argument.

The alternative would be to suppose, as De Motu 33 suggests,
that Berkeley holds that we gain a notion of activity, along with a
notion of spirit as substance, through reflective awareness/internal
consciousness:

[W]e feel it [mind] as a faculty of altering both our own state and
that of other things, and that is properly called vital, and puts a
wide distinction between soul and bodies. (DM 33)

On this interpretation, Berkeley would again have abandoned the
radical Humean position entertained in his notebooks, as he clearly
did on the question of the nature of spirit. One can only speculate as
to whether his reasons would have been primarily philosophical,
theological, or practical. Berkeley's writings, however, are not
generally characterized by deference to authority, quite the
contrary,[29]
as he himself proclaims:

… one thing, I know, I am not guilty of. I do not pin my
faith on the sleeve of any great man. I act not out of prejudice
& prepossession. I do not adhere to any opinion because it is
an old one, a receiv'd one, a fashionable one, or one that I have spent
much time in the study and cultivation of. (PC 465)

Nadler, S. (1998). “Doctrines of Explanation in Late Scholasticism
and in the Mechanical Philosophy.” In The Cambridge History of
Seventeenth-Century Philosophy (Volume 1). D. Garber and M. Ayers (eds.).
Cambridge: Cambridge University Press,
513–552.